The IPMon REST API is a robust and scalable solution built using Node.js, Express.js, and MongoDB. It provides a real-world implementation of a REST API with a database that persists data across server outages. The API endpoints remain the same as in the previous version, but now they are handled by an Express.js server. The API uses a web framework to handle HTTP requests and responses, making it more readable and maintainable. The MongoDB database is used to store IP address records, providing persistence of data. The API also includes utility modules for common tasks such as parsing, response formatting, error handling, and many more. The Express.js server listens on port 4000 and initializes the project by creating a directory named 'node-api' and initializing a new Node.js project with the default configuration. The `initialize` function is called when the server starts, which sets up the MongoDB client and defines API endpoints using Express.js methods. The `handleCreate`, `handleUpdate`, `handleShow`, `handleRead`, and `handleDelete` functions are used to handle requests to the API endpoints. These functions call internal helper functions such as `getGeolocation`, `insertRecord`, and `updateRecord`. The `getGeolocation` function is used to call the IP GeoLocation API to retrieve location details for each IP address, while the `insertRecord` and `updateRecord` functions are used to insert and update IP address records in MongoDB. With this implementation, the IPMon REST API service is complete, and it can be tested by running the 'server.js' file and using cURL utility to verify all API endpoints.